1. Field of the Invention
The present invention relates to an accumulator (gas-liquid separator) used for a heat pump-type refrigerating cycle (hereinafter called a heat pump system), such as a car air-conditioner, a room air-conditioner, or a freezing machine.
2. Description of the Related Art
As illustrated in FIGS. 7A and 7B, a heat pump system 200 making up a car air-conditioner or the like typically includes a compressor 210, an outdoor heat exchanger 220, an indoor heat exchanger 230, an expansion valve 260, a four-way switching valve 240 and the like, as well as an accumulator 250.
In such a heat pump system 200, switching (channel switching) between cooling operation and heating operation is performed by the four-way switching valve 240. During cooling operation, refrigerant circulates in a cycle as shown in FIG. 7A, and at this time, the outdoor heat exchanger 220 functions as a condenser, while the indoor heat exchanger 230 functions as an evaporator. During heating operation, refrigerant circulates in a cycle as shown in FIG. 7B, and at this time, the outdoor heat exchanger 220 functions as an evaporator, while the indoor heat exchanger 230 functions as a condenser. For both types of the operation, refrigerant under low temperature and pressure and in a gas-liquid mixture state is introduced from the evaporator (the indoor heat exchanger 230 or the outdoor heat exchanger 220) to the accumulator 250 via the four-way switching valve 240.
For the accumulator 250, the structure as described in Patent Document 1, for example, is known, including a bottomed cylindrical tank having an upper opening thereof that is hermetically sealed with a lid member provided with an inflow port and an outflow port, a gas-liquid separating member having an outer diameter smaller than an inner diameter of the tank and having an umbrella-like or an inversed thin-bowl shape, an outflow pipe having a double-pipe structure, including an inner pipe having an upper end that is joined to the outflow port and hanging from there, and an outer pipe, a strainer disposed close to the bottom of (the outer pipe of) this outflow pipe to catch/remove foreign matters contained in liquid-phase refrigerant and oil (refrigerant oil) mixed therein, and the like.
Refrigerant introduced into this accumulator 250 collides with the gas-liquid separating member to be diffused radially and to be separated into liquid-phase refrigerant and gas-phase refrigerant. The liquid-phase refrigerant (including oil) flows down along the inner periphery of the tank and is accumulated at a lower part of the tank, and the gas-phase refrigerant descends through the space defined between the inner pipe and the outer pipe in the outflow pipe (gas-phase refrigerant descending channel) and then ascends through the space within the inner pipe to be sucked from the suction side of the compressor 210 for circulation.
Oil accumulated at the lower part of the tank together with the liquid-phase refrigerant moves toward the tank bottom because of a difference in specific weight, properties or the like from the liquid-phase refrigerant, is sucked by the gas-phase refrigerant that is sucked from the suction side of the compressor via the outflow pipe, and then passes through (a net filter of) the strainer→an oil returning port formed at the bottom of the outflow pipe (outer pipe)→the space within the inner pipe of the outflow pipe and is returned to the suction side of the compressor together with the gas-phase refrigerant for circulation (see Patent Documents 2, 3 as well).
Meanwhile, when the operation of the system (compressor) is stopped, liquid-phase refrigerant including oil is accumulated at the lower part of the tank of the accumulator. In this case, when the oil used is not compatible with the refrigerant and has specific weight smaller than that of the refrigerant, they are separated into two layers due to a difference in specific weight and viscosity between the liquid-phase refrigerant and the oil, i.e., the oil layer is formed above and the liquid-phase refrigerant layer is formed below.
In such a two-layered separation state, when the system (compressor) is started, then the pressure in the tank drops rapidly, and so the liquid-phase refrigerant boils suddenly and vigorously (hereinafter called bumping), which causes loud impact noise unfortunately.
Presumably such a bumping phenomenon and the following impact noise are generated because of the following reason. Such a bumping phenomenon can be suppressed till some point due to the presence of the oil layer serving as the lid of the refrigerant layer (no bumping phenomenon occurs at the oil layer) even when the pressure in the tank (suction side of the compressor) drops during the starting of the compressor. However, if a difference in pressure between the above of the oil layer (the gas-phase refrigerant) and the below (the liquid-phase refrigerant) becomes a predetermined value or more, the liquid-phase refrigerant boils at once and explosively, and therefore these phenomena will occur (see Patent Document 2 also, describing a bumping phenomenon in the compressor).
Alternatively, when oil and liquid-phase refrigerant are not in a two-layered separation state as stated above during stopping of the compressor, i.e., when the oil and the liquid-phase refrigerant are in a mixture state during stopping of the compressor as well, or also in the case where the oil used is not compatible with the refrigerant and has specific weight larger than that of the refrigerant, and the liquid-phase refrigerant layer is formed above and the oil layer is formed below, the aforementioned bumping phenomenon where the liquid-phase refrigerant boils at once and explosively and the following impact noise may occur depending on the conditions, such as types of the refrigerant and the oil, and their properties.
As a measure to suppress such a bumping phenomenon and the following impact noise, the above-mentioned Patent Document 2 proposes the technique of providing an agitation blade at the rotating shaft (crankshaft) of the compressor including a reciprocating engine as a driving source, and rotating the agitation blade for agitation of the oil-layer part during starting of the compressor so as to discharge the liquid-phase refrigerant to the above of the oil.
Patent Document 3 proposes the technique of, in order to mix the oil and the liquid-phase refrigerant in a two-layered separation state reliably in (the tank) of the accumulator as a main purpose, blowing a part of the gas-phase refrigerant discharged from the compressor into the liquid-phase refrigerant for agitation from the bottom of the tank via a bypass channel having an open/close valve.
3. Related Patent Documents
Patent Document 1: JP 2014-70869 A
Patent Document 2: JP 2001-248923 A
Patent Document 3: JP 2004-263995 A